Sensitivity analysis of discrete periodic systems with applications to helicopter rotor dynamics

This paper presents a sensitivity formulation for periodic systems and a theoretical model for a helicopter rotor in forward flight. The formulation and the rotor model are validated by a few comparisons with other available methods and experimental values. The greatest advantage of the present sensitivity analysis is that the order of the Floquet matrix is independent of the number parameters to be investigated. This yields substantial savings in computation times over the existing methods. The formulation yields unique derivatives for the eigenvalues in spite of the nonuniqueness in the eigenvalues, and this includes also the frequency-locked region. The derivatives of the eigenvectors also follow from the same formulation except that it breaks down in the frequency-locked region.